As is well known, silver bromide is the light sensitive compound that is responsible for the production of all types of photographs. The silver bromide, a cream white solid, is dispersed in gelatin and the mixture is spread on the cellulose or film. In some cases, silver chloride and silver iodide may be used for special purpose films. After the film has been exposed, it is placed in a developing bath, for example hydroquinone, or some other reducing agent, to reduce the silver bromide to pure silver. This forms the negative. The film is now transferred to a stop bath to halt the action of the developer and then to a fix bath to dissolve the excess silver halide which receive no light. Typically, the fix bath, or fixer solution, commonly known as HYPO, is sodium thiosulfate. It solubilizes the silver halide to form a water soluble, silver thiosulfate complex. Eventually, the thiosulfate in the fixer becomes used and the fixing solutions must be replaced. There is, however, valuable silver in solution in the form of complex ions.
With the ever-increasing price of precious metals, it is desirable to recover the silver in metal form so that it may be sold. This is commonly done in industrial photography processes. However, with the ever-escalating price, it is desirable even for amateur photographers, to accomplish this. Most amateur photographers do not have access to large electrolysis units for electrolyzing spent fixing solution.
Accordingly, a primary object of this invention is to provide a small portable electrolysis unit for recovery of precious metals, especially silver, from waste solutions such as photographer's HYPO.
A further object of this invention is to provide only a portable, small electrolysis unit which may be conveniently used by home and/or amateur photographers, but provide a unit which is inexpensive, which facilitates recovery of silver as pure as 97% and to provide a unit which is economical to manufacture.
An even further object of the invention is to provide a portable electrolysis unit usable by amateur photographers which avoids the necessity for use of complex filtering systems or centrifuge systems to recover the majority of the silver plating out during the electrolysis process.
The method and manner of accomplishing each of these objectives, as well as others, will become apparent from the detailed description of the invention which follows.